Moment of Inertia

Moment of Inertia, I, is a measure of how the mass of a body is distributed about the axis of rotation. The greater the distance the mass is away from the object the larger the moment of inertia.

When a gymnast is twisting, he can extend his arms in front of him to slow rotation. This moves the gymnast’s center of gravity to somewhere in front of the body while also increasing the radius of the circle. By pulling his arms closer, he may If a gymnast leans forward or backwards in a pirouette, the center of gravity is somewhere outside the axis of rotation twist easier. Standing more vertically may also move the gymnast’s center of gravity closer. This may slow the pirouette or throw off the gymnast’s balance. Thus, the gymnast may adjust way his mass is distributed in order to obtain desired results or an adjustment of the moment of inertia may prove disastrous.